ClientServer Databases and the Oracle9i Relational Database

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Client/Server Databases andthe Oracle9i
RelationalDatabase
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Relational Database Terms

• Entity an object about which you want to store
  data
• Relationships links that show how different
  records are related
• Key Fields establish relationships among records
  in different tables
• Five main types of key fields
• primary keys
• candidate keys
• surrogate keys
• foreign keys
• composite keys

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Primary Keys

• Primary key
• Value must be unique for each record
• Serves to identify the record
• Present in every record
• Cant be NULL
• Should be numeric

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Candidate Keys

• Candidate key
• Any field that could be used as the primary key
• Should be a unique, unchanging numeric field

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Surrogate Keys

• Surrogate key created to be the records primary
  key identifier when no suitable primary key
  exists
• Surrogate key has no real relationship to the
  record to which it is assigned, other than to
  identify the record uniquely
• Developers configure the database to generate
  surrogate key values automatically
• In an Oracle database, you can automatically
  generate surrogate key values using a sequence
• Surrogate keys are always numerical fields,
  because the database generates surrogate key
  values automatically by incrementing the previous
  value by one

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Foreign Keys

• Foreign key a field in a table that is a primary
  key in another table
• Foreign key creates a relationship between the
  two tables
• Foreign key value must exist in the table where
  it is a primary key

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Composite Keys

• Composite key a unique key that you create by
  combining two or more fields
• Usually comprised of fields that are primary keys
  in other tables

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Personal Database Management Systems

• DBMS and database applications run on the same
  workstation and appear to the user as a single
  integrated application
• Personal databases used primarily for creating
  single-user database applications
• Support small multiuser database applications by
  storing the database application files on a file
  server instead of on a single users workstation
  and then transmitting the files or the parts of
  files containing the desired data to various
  users across a network
• Database developers should use a personal
  database only for non-mission-critical
  applications

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Client/Server Database Management Systems

• Client/server database
• Takes advantage of distributed processing and
  networked computers by distributing processing
  across multiple computers
• DBMS server process runs on one workstation, and
  the database applications run on separate client
  workstations across the network
• Preferred for database applications that retrieve
  and manipulate small amounts of data from
  databases containing large numbers of records
  because they minimize network traffic and improve
  response times
• Organizations generally use a client/server
  database if the database will have more than 10
  simultaneous users and if the database is mission
  critical

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Client/Server Database Architecture
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The Oracle9i Client/Server Database

• Oracle9i is the latest release of Oracle
  Corporations relational database
• All Oracle server- and client-side programs use
  Oracle Net, a utility that enables the network
  communication between the client and the server

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Client-Side Utilities

• SQLPlus
• for creating and testing command-line SQL queries
  and executing PL/SQL procedural programs
• Oracle9i Developer Suite
• for developing database applications including
  the following Developer tools
• Forms Builder
• for creating custom user applications
• Reports Builder
• for creating reports for displaying, printing,
  and distributing summary data
• Enterprise Manager
• for performing database administration tasks such
  as creating new user accounts and configuring how
  the DBMS stores and manages data

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Design Principles

• To avoid creating tables that contain redundant
  data, group related items that describe a single
  entity together in a common table
• Do not create tables that duplicate values many
  times in different rows
• When creating a database and inserting data
  values, you must specify the data type for each
  column
• Recall that primary key fields should use a
  number data type to avoid typographical,
  punctuation, and case variation errors

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The Clearwater Traders Sales Order Database

• Clearwater Traders
• Markets a line of clothing and sporting goods via
  mail-order catalogs
• Accepts customer orders via telephone, mail, and
  fax
• Wants to begin accepting orders using its Web
  site
• Has decided to offer 24-hour customer order
  service
• Existing microcomputer-based database system
  cannot handle current transaction volume
• Managers concerned that the current database does
  not have the failure-handling and recovery
  capabilities needed for an ordering system that
  cannot tolerate failures or downtime

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Clearwater Traders Data Requirements

• Customer name, address, daytime and evening
  telephone numbers, user names, and passwords
• Order date, payment method (check or credit
  card), order source (catalog description or Web
  site), and associated item numbers, sizes,
  colors, and quantities ordered
• Item descriptions and photo images, as well as
  item categories (womens clothing, outdoor gear,
  and so on), prices, and quantities on hand. Many
  clothing items are available in multiple sizes
  and colors. Sometimes the same item has different
  prices depending on the item size
• Information about incoming product shipments

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Clearwater Traders Table Relationships
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The Northwoods University Student Registration
Database

• Northwoods University
• Decided to replace its aging mainframe-based
  student registration system with a more modern
  client/server database system
• School officials want students to be able to
  retrieve course availability information,
  register for courses, and print transcripts using
  personal computers located in the student
  computer labs

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The Northwoods University Student Registration
Database (cont)

• Faculty members must be able to retrieve student
  course lists, drop and add students, and record
  course grades
• Faculty members must also be able to view records
  for the students they advise
• Security is a prime concern, so student and
  course records must be protected by password
  access

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Northwoods University Data Requirements

• Student name, address, telephone number, class
  (freshman, sophomore, junior, or senior), date of
  birth, PIN (personal identification number), and
  advisor ID
• Course call number (such as MIS 101), course
  name, credits, location, duration, maximum
  enrollment, instructor, and term offered
• Instructor name, office location, telephone
  number, rank, and PIN
• Student enrollment and grade information

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Northwoods University Table Relationships
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The Software Experts Project Management Database

• Software Experts
• Consulting firm that creates custom software
  applications
• Managers determine the number and the skill sets
  of the consultants that a given project requires
• Managers locate available consultants with the
  necessary skills
• One consultant is named project manager
• When completed, the project manager evaluates all
  the other consultants and all the consultants
  evaluate the project manager
• A project can be subdivided into multiple
  subprojects

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Software Experts Requirements

• Consultant information, including name, address,
  city, state, ZIP code, phone number, and e-mail
  address
• Descriptions of consultant skills
• Client information, including the client name,
  client contact name, and contact phone number

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Software Experts Requirements

• Project information, including the project name,
  the client associated with the project,
  associated subprojects, the project manager, and
  required skill sets
• Dates that a consultant started and finished
  working on a specific project and total days that
  the consultant spent working on the project
• Consultant evaluation information, including the
  date the evaluation was completed, who performed
  the evaluation, and the evaluation score and
  comments

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Software Experts Table Relationships
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Introduction to SQL

• Structured Query Language (SQL) the standard
  query language for relational databases
• Data definition language (DDL)
• Create new database objects
• Modify or delete existing objects.
• Data manipulation language (DML)
• Insert, update, delete, and view database data.

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Oracle9i User Accounts

• User account - identified by a unique username
  and password
• User schema - all of the objects that the user
  creates and stores in the database
• Object owner has privileges to perform all
  possible actions on an object

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Defining Oracle9i Database Tables

• To create a new table specify
• Table name
• Name of each data field
• Data type and size of each data field
• Constraints restrictions on the data values that
  a field can store
• Oracle Naming Standard
• Series of rules Oracle Corporation established
  for naming all database objects
• Objects must be from 1 to 30 characters long
• Can contain letters, numbers, and the special
  symbols , _, and
• Must begin with a character

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Creating a Table

• CREATE TABLE tablename
• (fieldname1data_type,
• (fieldname2 data_type,
• )

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Oracle9i Data Types

• Data type specifies the kind of data that a
  field stores
• Assigning a data type provides a means for error
  checking
• Data types enable the DBMS to use storage space
  more efficiently by internally storing different
  types of data in different ways

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Character Data Types

• VARCHAR2
• Stores variable-length character data up to a
  maximum of 4,000 characters
• Values in different records can have a different
  number of characters
• fieldname VARCHAR2(maximum_size)

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Character Data Types

• CHAR
• Fixed-length character data up to a maximum size
  of 2,000 characters
• Data values for different records all have the
  same number of characters
• DBMS adds trailing blank spaces to the end of the
  entry to make the entry fill the maximum_size
  value
• Data longer than maximum_size causes an error
• fieldname CHAR(maximum_size)

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Character Data Types

• NVARCHAR2 and NCHAR
• Analogous to VARCHAR2 and CHAR but use Unicode
  rather than ASCII
• Used to hold character data in languages other
  than English

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Number Data Types

• Stores negative, positive, fixed, and floating
  point numbers between 10130 and 10125, with
  precision up to 38 decimal places
• General Syntax fieldname NUMBER (precision,
  scale)
• Integer fieldname NUMBER(precision)
• Fixed point fieldname NUMBER(precision,scale
  )
• Floating point fieldname NUMBER

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Date and Time Data Types

• DATE
• Dates from December 31, 4712 BC to December 31,
  4712 AD
• Default format DD-MON-YY
• Default time format HHMISS A.M.
• fieldname DATE
• TIMESTAMP
• Similar to DATE but stores fractional seconds
• fieldname TIMESTAMP (fractional_seconds_precision)

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Date and Time Data Types

• INTERVAL YEAR TO MONTH
• Time interval, expressed in years and months
• 02-11 specifies a positive time interval of 2
  years and 11 months
• fieldname INTERVAL YEAR(year_precision) TO
  MONTH
• INTERVAL DAY TO SECOND
• Time interval, expressed in days, hours, minutes,
  and seconds
• -04 032032.00 4 days, 3 hours, 20 minutes, and
  32 seconds
• fieldname INTERVAL DAY(leading_precision) TO
  SECOND(fractional_seconds_precision)

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Large Object (LOB) Data Types
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Constraints

• Rules that restrict the data values that you can
  enter into a field in a database table
• Integrity constraints define primary and foreign
  keys
• Value constraints define specific data values or
  data ranges that must be inserted into columns
  and whether values must be unique or not NULL
• Table constraint restricts the data value with
  respect to all other values in the table
• Field constraint limits the value that can be
  placed in a specific field, irrespective of
  values that exist in other table records

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Oracle Constraint Naming Convention

• tablename_ fieldname_constraintID

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Integrity Constraints

• Define primary key fields
• Specify foreign keys and their corresponding
  table and column references
• Specify composite keys

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Value Constraints

• Check conditions field value must be a specific
  value or fall within a range of values
• NOT NULL constraints specify whether a field
  value can be NULL
• Default constraints specify that a field has a
  default value that the DBMS automatically inserts
  for every record, unless the user specifies an
  alternate value
• Unique constraints specify that a field must
  have a unique value for every table record

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Creating Database Tables Using SQLPlus

• Type SQL commands at the SQL prompt
• End each command with a semicolon ()
• Not case sensitive

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Log On to SQLPlus
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SQLPlus Program Window
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Create a Table
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Table Creation Sequence

• When creating tables with foreign key references,
  create referenced tables first
• Always create tables without foreign keys before
  those with foreign keys

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Using Notepad

• Useful to use Notepad to edit sql commands
• Commands can be edited without retyping
• Commands can be saved
• Saving multiple sql commands in a file creates a
  script

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Errors

• When an error occurs error information is
  displayed
• Line number
• Position on line
• Error code
• Description of error
• Error codes
• 3 letter prefix (I.e. ORA)
• 5 digit code
• More information on errors can be found at
  http//otn.oracle.com

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Exiting SQLPlus

• Three ways to exit SQLPlus
• Type exit at the SQL prompt
• Click File on the menu bar, and then click Exit
• Click the Close button on the program window
  title bar
• Database session ends when SQLPlus exits

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Create Table with Foreign Key Constraint
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Viewing Information About Tables

• describe tablename displays column names and
  data types
• Data dictionary tables that contain information
  about the structure of the database.
• USER shows the objects in the current users
  schema
• ALL shows both objects in the current users
  schema and objects that the user has privileges
  to manipulate
• DBA allows users who are database administrators
  to view information about all database objects

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Viewing Tables in the Database
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Viewing Constraints on One Table
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Modifying and Deleting Database Tables

• Modify existing database tables by
• Changing the name of a table
• Adding new columns
• Deleting columns that are no longer needed
• Changing the data type or maximum size of an
  existing column
• Unrestricted action some specifications can
  always be modified
• Restricted action specifications modified only
  in certain situations

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Unrestricted Action
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Restricted Actions
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Deleting and Renaming Tables

• To delete
• Drop table tablename
• Use with caution
• To delete foreign key constraints, add cascade
  constraints
• To rename
• Rename old_tablename to new_tablename
• DBMS automatically transfers to the new table
  integrity constraints, indexes, and privileges
  that referenced the old table.

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Adding Fields to Existing Tables

• To add a field
• ALTER TABLE tablename ADD(fieldname
  data_declaration constraints)

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Modifying Existing Field Data Definitions

• Can only change datatype to compatible data type
  (i.e. varchar2 to char)
• ALTER tablename MODIFY(fieldname
  new_data_declaration)

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Deleting a Field

• ALTER TABLE tablename DROP COLUMN fieldname
• Can be used to rename a field first drop, then
  add

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Adding and Deleting Constraints

• Add a constraint ALTER TABLE tablename ADD
  CONSTRAINT constraint_name constraint_definition
• Remove a constraint ALTER TABLE tablename DROP
  CONSTRAINT constraint_name

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Enabling and Disabling Constraints

• When modifying a database it can be useful to
  disable constraints
• Constraints are enabled by default
• To disable a constraint ALTER TABLE tablename
  DISABLE CONSTRAINT constraint_name
• To enable a constraint ALTER TABLE tablename
  ENABLE CONSTRAINT constraint_name

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Summary

• SQL commands include
• Data description language (DDL) commands create,
  modify, Deleted database objects
• Data manipulation language (DML) commands
  insert, update, delete, view database data
• To create a table
• specify the table name, the name of each data
  field, and the data type and size of each data
  field
• Data types ensure correct data values
• Constraints restrict values of database fields
• SQLPlus commands are not case sensitive

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Summary

• Errors include line number, position, error code
• Use DESCRIBE command to display a tables
  fieldnames and data types
• Tables can be modified or deleted but some
  changes are restricted